[SI-LIST] Re: uStrip question
- From: "Bill Dempsey" <bdempsey85@xxxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Mon, 8 Mar 2004 23:49:52 -0600
Tom,
We have a set of rt angle calibration connectors that we use to cal out the
coax + connector effect. These same "style" connectors (diff vendor) are
used as the souce/load connection point to the PCB. They are of course
soldered to the PCB -- that is to say they are not pressed or held in place.
Did I answer your question?
One item of note -- the Smith chart is showing a mostly inductive tline.
As part of this evaluation I built 3 tlines per board: one straight-thru,
one with five 0402 custom sized packages with the terminals shorted, and one
with five 0603 packages...
Interestingly the the tline with the 0603 pads (additional capacitance) has
much better performance (about 2.3dB loss vs. 6.5dB).
Bill
----- Original Message -----
From: "Tom Dagostino" <tom@xxxxxxxxxxxxx>
To: <bdempsey85@xxxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
Sent: Monday, March 08, 2004 10:26 PM
Subject: [SI-LIST] Re: uStrip question - repost
> What you did not mention in your note may be the problem you are having.
> How did you connect your VNA to the test articles? How clean was the
> launch? It is easy to get large reflections from poorly designed launches
> that will affect S21
>
>
> Tom Dagostino
> Teraspeed Consulting Group LLC
> Device Modeling Division
> 13610 SW Harness Lane
> Beaverton, OR 97008
> 503-430-1065
> tom@xxxxxxxxxxxxx <mailto:tom@xxxxxxxxxxxxx>
>
>
> Teraspeed Consulting Group LLC
> 2926 SE Yamhill St.
> Portland, OR 97214
> http://www.teraspeed.com
>
>
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Bill Dempsey
> Sent: Monday, March 08, 2004 7:57 PM
> To: bdempsey85@xxxxxxxxxxx; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] uStrip question - repost
>
>
> --sorry for the repost but the server is adding junk to the message that
> made it unclear to read --
>
> I recently built 3 different uStrip construction testboards and was
> surprised by the results: it didn't work!
>
> I built two boards as trace over copper with soldermask and one board
> as a co-planar waveguide. I constructed the geometries of the boards by
> following the results of some "freebie" tools out there.
>
> After the boards were built I connected them to an HP network analyzer
> (I calibrated out the cables/cons) to look at S21 response. What I
> found was surprising. The S21 was extremely poor: approx 6.5dB loss
> over 4". This just does not compare to the results of the tools I have
> access to. I expected about 1.2 - 1.5 dB of loss at this frequency.
>
> Has anyone else out there had some bad experiences with uStrip @
> 2.5GHz? What tools are you using? How are you correlating your
> tool's results to real-world?
>
> The construction of the three boards was as follows:
>
> Board 1: 12 mil trace, 1/2 oz foil with 1 oz plating, 8 mil to gnd (three
> sheets of 1080 prepreg), 1oz copper gnd
>
> Board 2: (CPW): 8 mil trace, 8 mils to gnd (again, 3 sheets of 1080
> prepreg), 6 mil to gnd return on signal layer, same plating/thicknesses
>
> Board 3: 4.75 mil trace, ~2.83 mils to gnd (one sheet of 1080 prepreg),
> 1/2 oz foil, 1oz plating, 1oz copper gnd
>
> Regards,
>
> Bill
>
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